1. Field of the Invention
The present invention relates, in general, to fluid conduits and, more specifically, to fluid conduit mounting apparatus.
2. Description of the Art
It is well known to flare the end of a fluid conduit to enable the end of the conduit to be easily attached to a suitable element, such as a valve, receiver, fitting, etc. In high pressure fluid conduits employed in vehicle brake and fluid lines, SAE standards require a double or inverted flared end on such conduits. In a double or inverted flared conduit, the end of the conduit is flared radially outward from the axial extent of the conduit and then an outer portion of the end is bent inward in parallel to and in registry with an outer surface of the flared end of the conduit to form a double flared wall at the end of the conduit with inner and exterior conical surfaces.
In a typical mounting arrangement, the double or inverted flared end of the conduit sealingly mates with a conically shaped seat in a female fitting, commonly referred to as a receiver. A bore in the receiver aligns with the bore in the conduit to form a fluid flow path therethrough. A male fitting is threadingly engaged with the receiver and also includes an internal conical surface which engages the exterior conical surface of the flared end of the conduit to urge the inner, folded over conically shaped flange of the flared end of the conduit into mating engagement with the conical seat in the receiver.
In the past, the fittings were made on lathes with rotating spindles such that the threads and the seal face or surface were machined on the same spindle. This method of processing produced concentric flare cone and thread center lines. However, current practice utilizes a more economical cold headed process for making the fittings and the separately processed rolled threads do not deliver the same high degree of concentricity as the more costly screw machine method.
The proper operation of such a fluid conduit fitting requires that the flared end of the conduit completely seat on the mating conical seat of the receiver about its full 360.degree. surface. This is not always possible due to the aforementioned use of the cold headed process which does not deliver the same high degree of concentricity as the screw machine method of forming such fittings and receivers. Further, traditional manufacturing tolerance of TIR (total indicated runout) can result in an eccentric alignment of the flared end of the conduit and the mating conical seat of the receiver, despite such parts being within their specified manufacturing tolerances. A large TIR can create a gap extending along a predetermined angular extent of the adjacent conical surfaces of the conduit and the receiver which causes leaks in the fluid system.
In the past, when a leak occurred, it was common to apply more torque to the fitting to forcibly urge the fitting and thereby the entire conical surface of the flared end of the conduit into engagement with the conical seat of the receiver. However, such additional torque is not always able to be easily applied to the fitting. In the past, sealing was obtained by utilizing a soft material for either the conduit or the internal flare seat in the receiver. Typically, the conical flare seat in the receiver was made of brass or, in later years, a brass seat insert was mounted in a steel receiver body. The softer brass material of the conical flare seat deformed under increased torque applied to the fitting to enable the flared end of the conduit to be forced into mating contact with the conical seat over the full 360.degree. extent of the conical seat despite any eccentricity which may exist between the flared end of the conduit, the conical seat or the axial alignment of the conduit with the conical seat in the receiver.
Newer receivers are formed primarily of steel, cast iron or anodized aluminum which are harder than brass typically used to form the conduit and not as deformable. Such receivers require higher torque to deform the flared end of the conduit into complete mating engagement with the conical seat of the receiver to form a leakproof annular seal between the mating surfaces thereof. Such increased torque is not always possible or desirable.
Similar problems arise in sealingly coupling a fluid conduit having an end flare constructed in accordance with International Organization Standardization Specifications ISO 4038-1977(E), hereafter "ISO". This type of end flare forms an enlarged, annular protrusion adjacent one end of the conduit which has a first angularly outwardly extending surface ending in an outer end at the maximum O.D. of the protrusion and a second, continuous, inwardly extending angular surface which terminates in a tip at one end of the conduit. The tip is designed to sealingly engage a conical seat in a receiver to sealingly couple the conduit to the receiver when a threaded fitting engages a threaded bore in the receiver and forcibly compresses the tip of the conduit against the conical seat in the receiver. If the surface finish of the tip of the flared end of the conduit and the conical seat in the receiver are sufficiently smooth and aligned, a seal can be made between the tip on the conduit and the conical seat in the receiver at relatively acceptable torques less than the yield point of the conduit.
In a fluid connector apparatus for an ISO flared conduit shown in FIG. 11, and 12 the included or open angle between opposed sides of the conical seat in the receiver is typically 120.degree.. The included or open angle between opposed faces of the second surface of the flared end extending from the tip is typically 115.degree.. As such, the metal to metal contact between the lip and the seat exists only along an annular ridge. Since the difference between the two diverging angles described above may vary between 1.degree. and 9.degree., it can be seen that it is difficult to create a seal between the flared end of the conduit and the seat in the receiver without distorting the conduit or the receiver.
However, if the sealing surfaces are not sufficiently smooth or due to variations in the diverging angles of the conical seat and the flared end of the conduit, or any misalignment or eccentric stackup beyond the clearance of the tube in the bore of the fitting, the only way that the flared end of the conduit can be sealingly joined to the receiver is to apply higher levels of torque to the fitting to distort the tip of the flare or to indent the tip into the conical seat in the receiver.
When such eccentricities or surface imperfections exist, a gap will be formed between the flared end surface of the conduit and the conical seat in the receiver under normal torque loads. The application of higher torques to close the gap and create a seal between the conduit and the receiver cause a thinning of the wall on the flared end of the conduit which creates the susceptibility to fatigue failure during the life of the conduit and/or fluid coupling.
Thus, it would be desirable to provide a mounting arrangement for two mating elements which includes a reduced resistance bead on the mating surface of one of the elements to form a leakproof seal when the two elements are brought together into forced engagement. It would also be desirable to provide a unique flared end on a high pressure fluid conduit which creates a leak free seal with a mating surface or seat without the use of additional seal elements, increased tightening torque, special tools or modifications to the mating fitting elements. It would also be desirable to provide a flared end conduit having unique means for forming a leakproof seal with a mating surface of another element, which means is integral with the conduit so as to always be present with the conduit, which eliminates any additional manufacturing operations required to assemble the seal, and which is formed of the same material as the conduit. It would also be desirable to provide a seal on the flared end of a fluid conduit which is deformed under normal or even reduced torque to account for eccentricity and angular variances between the mating surfaces of the fitting and the conduit end. It would also be desirable to provide a reduced resistance seal which is usable on a number of different fluid conduit end configurations including an inverted SAE flare, a modified O-ring face or an ISO flare. Finally, it would be desirable to provide a mounting apparatus, method and tool which provides a unique seal element on the flared end of a fluid conduit for forming a leakproof seal with a mating element which is manufacturable using conventional methods and techniques.